It's not even his nervousness or mannerisms that are so telling. His use of language reveals a great deal. All through the interview he constantly refers to his family as she, they, her, nobody. At one point he says, " and nothing, it's vanished, nothing was here, I mean," he is distancing himself from his family and referring to them almost like they are objects. The reporter catches this and asked their names. Only at that point does he use them. Murderers tend to dehumanize their victims not to face up to the guilt. He seems to do this all through the interview. He is using distancing language not expected from a grieving father and husband. He says nobody was here, the kids weren't here, she wasn't here. Her people, she, never her name until he is asked. After he says they had an emotional conversation he quickly adds, " I'll leave it at that," closing off the discussion. JmoYes and to suggest that someone would laugh after they know that their children are dead is way outside the realms of possibility to me. And if you laugh inappropriately when you should be grieving, you should seek help.
It is socially inappropriate.